H4 visa extension and stamping

[Susai]

The dependents are in offshore and current H4 visa is valid till December2013,
now my H1B extension is approved until 2016.
Question: -
1. If they travel now to USA by December2013, what will be the end date in i94 ?
2. Is it mandatory to have visa stamping done before they travel by December2013 to get approved until 2016.

[raghvi]

The dependents are in offshore and current H4 visa is valid till December2013,
now my H1B extension is approved until 2016.
Question: -
1. If they travel now to USA by December2013, what will be the end date in i94 ?
2. Is it mandatory to have visa stamping done before they travel by December2013 to get approved until 2016.

1. They typically should get I-94 to match with your extension petition that is 2016. But if they meet a strict officer they may get I-94 only till visa end date that is Dec 2013. Even if they get I-94 till Dec 2013, once in US you can apply for their extensions.
2. It is recommended but not mandatory.

This is my opinion not legal advice.